BEIRUT, Lebanon — An explosion targeted an American Embassy vehicle yesterday in northern Beirut, killing at least three Lebanese and injuring an American bystander and a local embassy employee, American and Lebanese officials said.

The blast, which damaged the armored SUV and several other vehicles, took place just ahead of a farewell reception for the American ambassador at a hotel in central Beirut.

No Americans were in the car, which was carrying two Lebanese employees of the embassy, a State Department spokesman, Sean McCormack, said in Washington. There were conflicting accounts of the death toll, with the State Department, from information provided by the American Embassy in Beirut, saying four people had been killed and Lebanese authorities saying that only three had died.

Secretary of State Rice called the bombing a “terrorist attack.”

“The United States will, of course, not be deterred in its efforts to help the Lebanese people, to help the democratic forces in Lebanon, to help Lebanon resist force and interference in their affairs,” she told reporters in the Saudi capital, Riyadh.

The bombing — which came as President Bush and Rice toured the Middle East — was the first attack on American diplomatic interests in Lebanon since the 1980s, when the country saw some of the deadliest terror attacks against Americans in U.S. history. A 1983 truck bombing killed 241 American service members at the Marine barracks at Beirut airport. The same year, a suicide bomber hit the American Embassy there, killing at least 17 Americans, including top CIA officials.

Prime Minister Siniora of Lebanon called an emergency Cabinet meeting after yesterday’s blast. The country has seen a series of bombings in the past three years targeting anti-Syrian figures, journalists and most recently, a top Lebanese army general.

The powerful blast could be heard across the Lebanese capital, sending gray smoke billowing over a Mediterranean coastal highway in the predominantly Christian Dora-Karantina neighborhood.

Two Lebanese employees of the embassy were in the vehicle, and the driver was lightly injured, Mr. McCormack said. He said four Beirut residents who do not work for the embassy were killed.

But Lebanese Red Cross Iyad al-Munzer said three people were killed. The figure was corroborated by two senior Lebanese security officials, speaking on condition of anonymity in line with military rules.

Five others were wounded, the officials said.

Among them was an American citizen, Minnesota native Mathew Clason, who was at the nearby National Evangelical Church near where the explosion took place. “The windows blew in and I fell down — I was knocked out. I don’t know exactly what happened,” Mr. Clason, who had been in Lebanon for two weeks, told AP Television News while sitting in the emergency room corridor of Jeitawi Hospital in Beirut. His head and right leg were bandaged.

The American Embassy immediately canceled a banquet for departing Ambassador Jeffrey Feltman, scheduled for yesterday evening at Beirut’s seaside Phoenicia Hotel.

A senior Lebanese police official said the blast was caused by a bomb placed between two garbage containers on the side of a narrow road adjacent to the main highway, which detonated as the car passed.

Mr. McCormack could not offer specifics about the blast or whether the vehicle had been targeted, but said it was hit directly “by the explosion itself.” He said agents from the State Department’s Bureau of Diplomatic Security would work with Lebanese authorities to investigate the blast and that the American Embassy in Beirut was reviewing security.

Beirut has had a long history of attacks against Americans since the turmoil of the 15-year civil war, which ended in 1990.

In 1976, the American ambassador to Lebanon, Francis Meloy Jr., and an aide, Robert Waring, were kidnapped and shot to death in Beirut. In 1984, William Buckley, CIA station chief in Beirut, was kidnapped and murdered by the Islamic Jihad group. America withdrew all diplomats from Beirut in September 1989 and did not reopen its embassy until 1991.